665287681 has 2 divisors, whose sum is σ = 665287682. Its totient is φ = 665287680.

The previous prime is 665287669. The next prime is 665287697. The reversal of 665287681 is 186782566.

665287681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 474847681 + 190440000 = 21791^2 + 13800^2 .

It is a cyclic number.

It is not a de Polignac number, because 665287681 - 2⁹ = 665287169 is a prime.

It is a super-2 number, since 2×665287681² = 885215396980715522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (665287981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332643840 + 332643841.

It is an arithmetic number, because the mean of its divisors is an integer number (332643841).

Almost surely, 2^665287681 is an apocalyptic number.

It is an amenable number.

665287681 is a deficient number, since it is larger than the sum of its proper divisors (1).

665287681 is an equidigital number, since it uses as much as digits as its factorization.

665287681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 967680, while the sum is 49.

The square root of 665287681 is about 25793.1712086746. The cubic root of 665287681 is about 872.9777214881.

The spelling of 665287681 in words is "six hundred sixty-five million, two hundred eighty-seven thousand, six hundred eighty-one".